Railway control system



June 5, 1962 L. D. BARRY RAILWAY CONTROL SYSTEM 8 Sheets-Sheet 1 Filed Oct. .3, 1955 June 5, 1962 D. BARRY RAILWAY CONTROL SYSTEM 8 Sheets-Sheet 2 Filed Oct. 3, 1955 INVENTOR.

June 5, 1962 D. BARRY RAILWAY CONTROL SYSTEM 8 Sheets-Sheet 3 Filed Oct. 5, 1955 INVENTOR.

Awww www www June 5, 1962 D. BARRY RAILWAY CONTROL SYSTEM June 5, 1962 L. D. BARRY RAILWAY CONTROL SYSTEM Filed OCT.. 5, 1955 June 5', 1962 L. D. BARRY RAILWAY CONTROL SYSTEM 8 Sheets-Sheet 6 Filed 0G13. 3, 1955 INVEN TOR.

ww .Ewh E ummm June 5, 1962 D. BARRY RAILWAY coNTRoLsysTEn/I 8 sheets-sheet 'T Filed Oct. 3, 1955 IN V EN TOR.

June 5, 1962 1 D. BARRY 3,037,461

RAILWAY CONTROL SYSTEM Filed 0G13. 3, 1955 8 Sheets-Sheet 8 IAWENTOR. MMI Z?. W

United States Patent O 3,037,461 RALWAY CNTRL SYSTEM Leonard D. Barry, 1930i) Pennington Drive, Detroit 21, Mich. Filed Det. 3, 1955, Ser. No. 538,058 62 Claims. (Cl. 11M- 132i This invention relates to contact control systems and in particular to a railway system for coupling and uncoupling cars at operating speeds and for controlling speed differences between cars or trains whereby they can safely couple, uncouple, or closely follow each other at speed.

This is a continuation-in-part of my abandoned application Ser. No. 146,767 on Railway Control System for Coincident Local and Express Service and is directed toward the control circuits Iand improvements thereof.

The control circuit between trains described in the above mentioned application and disclosed in improved Iand yariouts forms herein can be represented briefly as a circuit including a shunt or separately excited dynamo or other suitable voltage supply arranged on each of two or more vehicle units developing an output representing vehicle speed and connected in parallel by trackway conductive means between vehicles, and automatic accelerating `and decelerating means on the vehicles arranged to accelerate or decelerate the vehicle respectively according to whether the vehicles tachometric voltage supply device or dynamo in this circuit is functioning as a receiver or generator and according to the operators direction, whereby the operators control, or normal operating speed, is subject to conditions if safety and whereby the speed and various other -functions for coupling and un- .coupling at speed are controlled automatically.

The length of the control circuit between trains is limited by insulators and block circuits which control the bridging of the insulators so that the range or zone of the control always extends a safe distance ahead of or behind the train. Whenever this control circuit is cornpleted between trains the trains are controlled to a safe speed difference.

An object of this invention is to provide a contact control system whereby a train can safely couple and uncouple cars at speed on the same stretch of track or anywhere along the trackway without the train being needlessly slowed. A further object is that these controls enable the train to accelerate a car or train ahead at the same time a car is uncoupled from the rear and slowed.

It is an object that the contact system distinguish an approaching from a receding train, so that when a car or unit is uncoupled from the rear of a train, for example, the unit can be slowed and stopped without causing the train to be slowed or without disrupting the control circuit and yet permitting the train and car to maintain control between other vehicles within the range of control. As another example, it is desired that trains in the same zone of control can he independently acceierated by the operators controis either or both away from the other and maintain control with any vehicle they approach. It is an object to limit acceleration to the direction away from an approaching vehicle in the zone of control.

lt is an object to provide a polarized control current to distinguish a faster moving from a slower or standing vehicle; and, if two directional operation is desired, to provide a polarized control voltage to represent direction of Vehicle movement; and further, to polarize the transmission system of the `control current to distinguish an approaching from a receding vehicle; and to polarize the vehicles control circuits and, if two directional operation is provided, to connect these circuits through contacts on the vehicles reverse switch to select proper control.

"ice

It is an object of this invention to polarize vthe control circuit between trains to provide signaling between trains traveling in the same direction when the faster moving tnain is in the rear and to block signaling therebetween when the slower moving train is in the rear.

In accord with this invention Various rectifier or circuit polarizing arrangements are provided in the control cirfcuit along the right-of-Way or both along the route and on the vehicles. It is a further object to overcome any limitation which these polarizing arrangements may impose where it is desired that the speed of a rail unit be limited by a rail unit therebehind, so that the forward unit can be reached and coupled more readily or assuredly without running away.

'It is an object to replace the stopping zone as disclosed in my above mentioned application with a control circuit having rectifers arranged to limit the direction of control current along the control conductors between vehicles, so that only a slower forward and faster rearward train will pass a control current. The stopping zone, on the other hand, is a section of trackway where the control circuit is open between vehicles however close and re quites for safety that the trackwtay be clear except for a train and a unit uncoupled therefrom.

lf intertrain control circuits were completed on every :car a train of one car approachingr a train of ten cars would send a current and the cars of the other train would each receive approximately one-tenth of this current, or each car of a ten car train approaching a standing car at the same speed difference would each send approximately a tenth of the same current to the car. Thus the more cars in a train relative to the number of cars in a train in intercontrol therewith the smaller and less effective the control current would be on the larger train. lt is therefore desired that just one intertrain control circuit per train be closed. Accordingly the control circuit is connected through the cars reverse switch and through coupling switches.

To prevent control between two cars when one uncouples `from the other and each has its control circuit completed to a single control line, rectitiers are spaced between lengths of the control line at less than the interval between control circuit contact points between the two cars when coupled. It is a further object to reduce the number of these rectifiers or other polarizing mc-ans needed along the right-of-way by providing a period in which the control circuit on the uncoupled car or unit is fully or partially opened so that it will not receive signals from the faster moving forward train even when connected -by the same .section of the control conductor. It is an object to automatically slow a unit uncoupled at speed to increase the distance to the forward train to include a minimum of one rectifier in the control circuit between trains before the time interval of open control ends. Automatic slowing of an uncoupled unit when its control circuit is open is important. It is therefore a further object to provide safety means to check before unconpling is permitted that there is no train within the zone of control that would not be in intercontrol Where needed for safety. It is a further object to stop any traiic which after the unit is uncoupled might enter the zone of control at the rear of an uncoup-led unit that does not receive control current, approaching traffic being stopped by signaling or by shorting the control conductors.

It is a further object to ground the control circuit of f the control line conductor relative to all traffic approach ing any danger condition or defective portion of the control circuit. Another object is to provide means to prevent a train from being automatically accelerated or from being accelerated at an unsafe speed toward a forward spezial train by an approaching rearward train. Some other bjects of safety are to provide check circuits to detect a car that has no control circuit or an open control circuit to warn or stop approaching trains, to check the control circuit including important connections such as the bridging of the control blocks and electrical contact between the control conductors and current collectors on the vehicles, to stop a train whose control or check circuit is open or defective, and to warn or stop trains approaching a defective control block.

Another object is to arrange this intertrain control circuit to utilize a power distribution contact conductor for control signaling or, in other words, to arrange that the control line be suited as the power line for electric traction.

Another object is to provide control circuit arrangements for either insulated or noninsulated rails; so that advantage may be taken of existing track circuits, the trolley wire need not be divided into blocks, or the control circuit can be utilized even where rails are not insulated apart as in street-railway service. Variations are accordingly provided: one in which the rail and control conductor are both insulated into blocks or sections, others in which either only the rails or only the control line conductor are divided into blocks for limiting the zone of control between trains.

Some of the other and further objects are: to provide a contact control system to accelerate a car ahead of a train to coupling speed subject to the desire of the operator on the car ahead; to stop or slow a train to coupling speed before reaching a standing or slower moving car; to provide an optionally selectable delay of stopping when the intertrain control circuit is rst completed with a strong stopping current and a continuous check of the reduction of this stopping current according to the distance traveled during the delay period whereby if the current does not reduce suicinently the brakes are applied; to limit the magnitude of the control current so that the control current will not be excessive where large speed diierences exist; and to dependability, safety, and convenience of operation.

A general object for these controls is to reduce needless automatic slowing of the train or car when conditions are safe.

These controls are such that they can be utilized for accelerating multiple unit cars ahead of a train of these cars to safely couple therewith at speed, to couple and uncouple cars on the rear of a train at speed, to prevent coupling or collision, and to control the speed of vehicles paralleling a train at speed to permit transfer therebetween. The word track is meant to include parallel tracks and control conductor to mean parallel and electrically connected control conductors where the controls are installed for speed control between vehicles on parallel vehicle ways.

All or a number of these and other objects are obtained in cooperation in the variations of this invention described hereinafter with reference to the accompanying drawings wherein:

FIGURE l is a diagrammatic view of a trackway along which are control-circuit and trackway blocks and differential check circuits each controlling a train stop and signal lamp, and on which a train and car uncoupled therefrom are shown with their intertrain control circuit.

FIGURE 2 is a diagrammatic view of control circuits on a multiple-unit car arranged to operate over the system illustrated in FIGURE l.

FIGURE 3 is a perspective view of two of the operators control levers showing interlocking therebetween.

`FIGURE 4 is a diagrammatic view of a trackway on which are a train and a car which has uncoupled therefrom with portions of their control circuits cooperating with a single-control-conductor-block arrangement for noninsulated rails.

FIGURE 5 is a diagrammatic view of a trackway and i vehicles thereon with circuits arranged for transmitting A.C. speed control currents on a traction power contact line.

FIGURE 6 diagrammatically illustrates a three-rectier synchronous rectifier.

FIGURES 7 and 8 illustrate diagrammatically two combined control and power contact-conductor blockbridging arrangements for the A.C. control circuit of FIGURE 5.

FIGURE 9 is a diagrammatic view of a trackway and vehicles thereon showing a variation of the intertrain control circuit in which alternate half cycles are passed and in which a bucking generator is used to prevent passage of traction current through the control circuit.

FIGURES l0 and l1 schematically represent operation of wattmeters in an intertrain control circuit, FIG- URE ll showing how a wattmeter can give a false indication.

FIGURE 12 is a diagrammatic view of a more com plete car and trackway A.C. control than those shown in FIGURES 5 and 9 and in which direction of train movement is checked before permitting acceleration in the direction set bythe reverse switch.

FIGURE 13 is a diagrammatic view of a control circuit between two cars illustrating a rheostatic arrangement which can be used, though not preferred, in place of the D.C. or A.C. dynamo.

FIGURE 14 illustrates how A.C. traction power can be supplied on a D.C. control conductor and separated on the trains.

FIGURE 15 is a diagrammatic view of a trackway, a train and an uncoupled unit thereon, and circuits of a two-control-conductor system for interrupting control between the train and unit while maintaining control with other trains within the zone of control.

FIGURE 16 is a diagrammatic View of more complete control circuits on a car of FIGURE l5 showing a variation of the speed controls over those shown in FIGURES 2 and l2.

Tmckway Control Divisions and Bridging Referring to the drawings and in particular to FIG- URES l and 2, along track 10, FIGURE l, having rails 11 and 12 is run control conductor or line 14. Line 14 is a rail or Wire contact conductor insulated from ground and supported similarly as third rail or trolley wires in electric traction. All or a portion of line 14 can be divided into segments 16 by insulators 18. Multiple-unit cars 20, 21, and 22 on track 10 have current collectors or trolleys 24 engaging control line 14 connecting an intertrain control and a check circuit between line 14 and the rails. Segments y16 are shown shorter than the spacing ybetween collector shoes or trolleys 24 on different cars when coupled. Adjacent sections or segments are each separated by a rectier 26 arranged to pass a current from left to right from section to section along the control line 14. A series of segments are electrically connected to line 28 in which the rectiiiers 26 which are between these segments are conveniently located with a condenser 3i) across their terminals to pass an A.C. check current and a current for closing a two-Way signal circuit.

Control blocks A and B, represented in FIGURE l each as a series of control line segments, and block C, which is not divided into segments, are arranged to be electrically connected or bridged together for a safe distance between trains. Block A is bridged to B and B to C etc. each through a rectifier 26 in series with an A.C. choke 32 and back contacts on either or both control-line-block bridging relays BR and BRI the back contacts of which are in parallel. Similarly other blocks not shown are connected along the trackway. A rectier connection between blocks or segments of blocks is called a rectier bond.

Rail 12 is divided in the usual manner by insulators 36 into track circuit blocks A, B', and C' of substantially the same length and as part of control blocks A, B, and C respectively and displaced to the left relative to the control blocks equal to the distance from the engaged current collector to beyond the front wheel contact points on the vehicle on which this distance is greatest. Where line 144 is a third rail and trolleys 24 are shoes placed endward beyond contact points of the car wheels the control line blocks and track circuit blocks can be coextensive (no displacement needed). Across rails 11 and 12 at the left-hand end of each block a secondary coil 38 of supply transformer 4t) is connected preferably as shown to supply reverse polarity on adjacent blocks. Across rails 11 and 12 at the right-hand end of each block the coil of a track circuit relay TR is connected.

Track circuit relays TR control the bridging relays BR and BRl so that whenever the track circuit is shorted a number of control blocks either to the right or left or in both directions along the track are electrically connected together. Rail i1 being free from insulators is the return conductor for the control circuit between trains. lf both rails have insulators the insulators can be bypassed by the usual impedance bonds or as shown in FIGURE l1 by rectier bonds or by relay bridges across insulated track joints in one rail.

The coil of relay BR between blocks A and B is connected through a circuit comprising in series secondary 42 of transformer 40 block C', line 43 opened through front contacts 44- of relay TR in block B' and closed through front contacts 45 of relay TR in block A', and the coil of relay BR between blocks A and B to ground. Thus a car shorting the rails of block B' will drop relay TR therein dropping relays BR at each end of block B bridging control line sections A, B, and C together. Other blocks are similar to block B.

To increase the number of blocks bridged together upon shorting a track circuit block, each line 43 can be extended through other front contacts on relays TR in a series of adjacent blocks, whereby a solid group of blocks are bridged whenever a relay TR is dropped. To bridge blocks in the opposite direction from. a

train, secondary 42 of transformer 4t? block B is connected by line 46 through front contacts 47 of relay TR block A' to relay BR between blocks B and C. To increase the number of blocks bridged by line 46 this line can be extended to include one or more other front contacts on relays TR in a series of blocks, whereby a solid group of blocks are bridged in both directions from a shorted block. The zone of control between trains is limited by the maximum number and length of the blocks bridged together by the shorting of each track circuit block. Three to four blocks is the variation of the zone control between trains with the arrangement shown in FIGURE l. Each extension of line d?) or 46 to include another pair of front contacts of the next relay TR is an additional block bridged by the shorting of a block.

Check Circuits AC. check circuits run from one end of fone control block to the far end of the next block and include the bridge contacts between blocks to insure that the blocks are properly connected together. They also check the control line and control line grounding lines for breaks and shorts, check the control circuit on the cars and give warning or stop the train when not receiving check `current, check if there is a car on the track having no automatic controls or open control circuit, and short the control line within the Zone of control relative to trailic approaching a shorted or open track circuit block when either the A.C. check current of the control block associated with the shorted or open track circuit block or the adjacent control block to the left is not reduced by check current drained from the control line through one or more car control check circuits or when the check current is absent. The control line check circuit of block B comprises in series coil 48 of transformer 40 in block B', the left-hand coil of differential relay DCR at the opposi-te end of block B', attenuator 50 arranged to block all but the check current to the output side of rectifier 26 between blocks A and B, back contacts of relays BR or BRl between blocks A and B, line 28 block B and condensers 3G therein, segment 16 at the right-hand end of block B, line 52, attenuator S3 arranged to block all but the check current, coil of sensitive relay SCR, signal light 54 which indicates that the check circuit is completed, right-hand coil of differential check relay DCR, rail i2 to coil 48, all in block B'.

The intertrain control `circuit between car 22 and train 20-21 comprises briefly on each unit trolleys 24 connected by line 56 between coupled cars, segment 57 of traction motor reverse switch REV connecting coupling switch SC closed on the front `of cai 22 and train Ztl- 21, AC. choke coil 58, resistor 59 across which currentdirection-polarized automatic car controls ACC are connected through reverse switch 60 reversed when the cars are moving in the opposite direction on track 1t), dynamo DYN developing a voltage representing car speed, all in series across control line 14 and the rails. This intertrain control circuit is similarly connected in parallel across line 14 and ground return rail 11 by each train having this control. The faster unit 2tl-21 generates a control voltage blocked by rectifiers 26 from passing current to car 22 uncoupled therefrom and slowed. 'If the `faster unit were behind, the dynamo in the control circuit thereof would act as a generator supplying current to the dynamo of the slower unit operating as a motor. Automatic car controls ACC determine whether the dynamo is generating or motoring and according to the current provide safe and desired control automatically.

Each car has an A.C. check circuit completed on each train across the `control line and rails via the trains intertrain control circuit. The check circuit through each train, as shown in FIGURES l and 2, utilizes a portion of the trackway check circuit described and the portion of the trains control circuit to be checked by current in this circuit. The check circuit for either train of FIG- URE l comprises coil 48 of transformer 40 block B', the left-hand coil of relay DCR at the opposite end of block B', attenuator Sti, back contacts of relays BR and BR1 in parallel between blocks A and B, line 28 block B, trolley 24 of each train in block B, and on each train (referring to FIGURE 2) segment 57 of reverse switch REV, contacts 86 of coupling switch CS, line 88, line 62 from the trolley side of choke 58, back contacts of relay COR which is energized for a while after the car is uncoupled from a train, a Vseries-parallel tuned circuit 63 arranged to pass the check current Vand block other frequencies, and full-wave rectifier 64 with the coil of check relay CR connected across its output terminals back to line 88 on the other side of choke 53, resistors 90 and 59 in line 88, dynamo DY N to rails 11 and 12 to the other side of coil 48 in block B. The opening of this A.C. check circuit by relay COR or otherwise, as by a broken wire or open trolley circuit, enables, as will be explained, a sole car or unit shorting a track circuit or adjacent track circuits to automatically stop appreaching trains having the automatic controls of FIG- URE 2. Track relays TR can also control a usual type of signaling for trains not having this automatic control circuit.

Control line sections are grounded and stop signals can be set whenever a check circuit indicates a dangerous condition. Block B is arranged to be grounded through line 52 above attenuator S3 to ground rail il through a circuit'comprising in series A C. choke 66, and'either back contacts of relay VSCR block B to rail il or in paralylel back contacts of relay TR block B, back contacts of differential relays DCR of blocks B and A all in series to rail 11. The control line ground is similarly connected in other blocks. The inclusion of back contacts of relay DCR block A together with the displacement of the track blocks relative to the control blocks prevents the shorting of the control line by a train extending into two blocks when drawing check current from only one of these blocks. Where line 14 is a third rail, for example, and all power vehicles have third-rail shoes engaging line 14 at both ends of the vehicle endward of the contact points of the wheels, the grounding lines for control line 14 need not be connected through back contacts of differential relay DCR in the block to the left of the shorted block but preferably only through back contacts of relays TR and DCR in the same block with line 52.

When there is no trahie near, relays DCR and SCR are deenergized, since the check circuit is opened by the energizing of both relays BR and BR1 between two blocks by the energizing of several track circuit relays TR in adjacent blocks. Then, as a train approaches, the control blocks are bridged ahead of the train by the dropping of relays BR or BRI according to the direction of travel, closing check circuits, energizing relays DCR and SCR ahead of track circuit blocks shorted by the train. When a train whose check circuit is closed enters a control block the check current reaching relay SCR is reduced, but relay SCR remains energized and open, being designed to hold up `for a maximum number of trains that might be in the block, only a broken wire or true short being suhcient to drop relay SCR. The current through the right-hand coil of DCR is decreased when check current of that block is drawn by one or more trains, because that coil of relay DCR is now in parallel with the trains check circuits. The current through the left-hand coil of DCR is increased, being the sum current of the check currents drawn by trains in that vblock plus the current passing through the right-hand coil of DCR. Therefore a train having its control circuit closed draws a check current which opens relay DCR as relay TR of the same block drops. Relay DCR is arranged to open before relay TR has had time to drop. Therefore, because relays DCR and SCR `are energized and open when TR drops, the control line is not grounded. Line 56 connecting trolleys 24 between coupled cars enables the trains check circuit completed on the lead car to take check current from each control block engaged by a trolley 24 of the train. Relays DCR are thereby opened in each control block engaged by a connected trolley 24. It is desired that each track block be cleared before the train stops drawing check current therefrom; `accordingly trolleys or collector shoes 24 can be placed endward of the wheel contact points of each car or of the end cars; or, where only one trolley per car is provided, the track circuit blocks are preferably displaced relative to `the control blocks as shown `and explained, so that a car unshorts a track block before it stops drawing check current from the control block associated therewith or for the reverse direction of travel the car closes the check circuit of a particular block before shorting its rails. Train 2-0-21 which is drawing check current from block B and has shorted block C with its forward wheels and axles without drawing check current from block C does not close the control-line grounding circuit, because relay DCR block B has opened the grounding circuit of block C; but when the trolley of car 21 passes into block C, unit 22, not drawing check current for a time period after uucoupling, allows relay DCR of the block which unit 22 shorts to drop. lf a train does not ground a check current (indicating that the control or check circuit is not completed on the train) and with the adjacent block to the left unoccupied all other traiiic approaching the shorted block will be halted by the grounding of the control line within the zone of control. A. train which yfails to receive a check current through its check circuit will be halted by its relay CR dropping. When a unit is uncoupled from a train at speed it is then only necessary to open the check circuit on the unit to slow the unit and halt approaching tratiic without elfecting the speed of the train from which the unit uncoupled, since the train is then receding from the unit and rectificrs 26 prevent control between receding vehicles as will be explained,

T wo-Way Signaling Control to either a faster or slower forward vehicle, i.e. two-way control signaling, is provided by bypassing rectifiers 25 through front contacts on relays TCR whenever an A.C. current of frequency F1 selectably supplied from a train is received by one of these relays. A coil of each relay TCR is connected to the D C. ends of full-wave bridge rectifier 70. One A.C end of 70 is grounded, rail 11 being a common for all grounds, and the other A.C. end is connected in series with a seres-parallel-tuned frequency-selective circuit 71 to line 28. Circuit 71 passes frequency F1 sent from a train moving from left to right to close relays TCR ahead of the train and establish a two-way control circuit. Each block section of line 14 having segments 16 connected through rectifiers 26 has a line 72 connecting segments 16 at opposite ends of that block. Line 72 is connected from the output side of rectifier 26 at the right-hand end segment of block B in series with A.C. choke 73 and front contacts on relay TCR block B to beyond the last rectifier 26 at the lefthand end of block B. Chokes 32 and 73 prevent A C. check current from passing from one block to another. Choke 73 and front contacts of relay TCR are bypassed by wideatuned band-pass circuit 74 designed to block the control-line-check and intertrain-control currents and to pass three different frequencies including F1 which circuit 71 passes to close relays TCR in chain succession in the portion of the zone of control to the right of the first block receiving F1 from a train. Thus lines 28 and 72 form a current loop in each block when contacts of TCR of that block are closed whereby control current from any segment in the block can traverse the loop to any or all segments within the block and whereby all rectifiers 26 which were bridging control blocks together ahead of but not behind the train traveling from left to right are bypassed for two-way conduction.

For operation in the reverse directon the trains send frequency F2 which is not passed by filters 71 but which is passed by circuits 74 to close relays TCR in succession by energizing another coil thereon. This coil is connected to terminals of full-wave bridge rectifier 76. One A.C. end of 76 is grounded, the other connected in series with frequency F2 selective pass circuit 78 to line 26 in the next block to the right of TCR. Thus relays TCR are closed in either direction from a train to the end of the zone of control depending ou frequency Fi or F2 being sent from a train, whereby a unit can be uncoupled and slowed from a train at speed with the control current blocked by rectiers 26 between the train and unit to prevent the unit from slowing the train even while the train sends the signal F1 or F2 bypassing rectifiers 26 in the zone of control ahead of the train to limit the speed of a forward unit to couple it.

Alternators F1 and F2' on the car FIGURE 2 supply respectively frequencies F1 and `1572 either of which can he manually connected to line 14. Alternator F1 or F2 is connected to trolley 24 by a circuit following the check circuit from trolley 24 through back contacts of relay COR, and from there in series normally open contacts 79 of operators switch 80, `Fl-FZ selector switch 81 (hand operated) to alternator F1 or F2 respectively in series with frequency F1 and F2 limited pass filters 82 and 83 to ground. By connecting F1' or F2 to line 14 through contacts on COR the operator on an uncoupled unit cannot slow the forward train by establishing two-way control therewith during the time delay period in which relay COR is open.

Intel-train Control Circuit on Vehicles Referring to the car control circuits FIGURE 2, the intertrain control circuit on this vehicle, arranged for operation in either direction on track of 'FIGURE 1, is connected from collector 24 engaging control line 14 to rails 11 and 12 in series with segment 57 on the traotionpower reverse switch REV to contacts 86 on coupling switch CS or CS whichever is at the Ifront of the vehicle as determined by the position of REV, line 88, A.C. choke coil 53, resistor 90, resistor 59, current limiting series field 92 and armature of D.C. dynamo DYN in series to Wheels and rails. Coupling switches SC and SC located on opposite ends of each car are of the spring return push button type arranged to be pressed open between coupled cars and closed at the ends of the train. lectrical connections to be made on either the front or rear car of a train are connected through the coupling switch at respectively the front or rear through contacts on reverse switch REV the position of which determines which end of the train is front. This main control circuit is there- `fore closed on the yfront car only of units or trains of one or more of these cars.

Dynamo DYN is preferably driven at a speed proportional to the r.p.m. of the car wheels 94 through positive drive 95 and is excited from vehicle control-power battery 96 or other dependable supply. As an alternative the dynamo could be driven at constant speed with ield eX- citation dependent on the speed of the car; or the control circuits can be adapted for an A C. dynamo, as shown in. FIGURES 5, 9, 10, 11 and 12, or replaced with a rheostatic voltage divider, as shown in FIGURE 13. In any case the voltage output of the units vary with speed, and the output voltage is the same for all vehicles at the same speed with zero control current except when the voltage is adjusted to balance or reach Zero control current at a safe speed difference. Current direction through the cars control circuit determines whether the car should be stopped or accelerated. When the dynamo is generating, the control current for that vehicle is called a stopping current, and when motoring, the control current is called an accelerating current. The potential fed by DYN to the control line is selected to be positive when the car is traveling from left to right and negative when traveling from right to left on track 10. Whenever a sufficient control current flows from car 22 to control line 14 and down through a car of unit -21 with cars moving from left to right car 22 is to -be slowed and/ or unit 2li-21 accelerated until the voltage difference between units is balanced to zero at a safe or zero speed difference. An adjustable resistance 98 bypassed by normally closed contacts 99 of operators switch 80 is in series with the main field 101 of dynamo DYN to enable the operator by opening contacts 99 to insert resistance 98 reducing the eld and voltage of DYN so that the voltage difference between his train and the forward unit is balanced out at a speed ditierence at which his train approaches the unit for safe coupling. This balancing speed diierence is adjustable by varying resistance 93 as desired.

The current limiting series iield 92 opposes the main iield when dynamo DYN is generating, i.e. passing a current in the direction of its generated current, thereby reducing the output voltage; and field 92 aids the main iield when the dynamo is motoring, thereby increasing the back electromotive force generated. By providing series fields 92 the intertrain control current is reduced by both the generating and motoring dynamos. This is the preferred means to limit the maximum control current and reduce the operating voltage range required of the intertrain control circuit relays.

W' n the direction of car operation is reversed over :une track both the polarity of DYN and connection of car controls to the intertrain control circuit are reversed, so that trains traveling in opposite directions toward each other will be stopped and so that the same trackway control circuits can be used for both directions of traiiic.

The polarity of DYN is reversed by reversal of rotation of the cars wheels. To provide for a Vcar being turned around, the main iield of DYN is connected through reverse switch 102 across the positive of battery 96 and its negative ground return. Line 103 connects the positive of battery 96 to reverse switch 102. Reverse switch 10-2 is actuated by any suitable actuator such as 104 which is pivoted for movement in a transverse plane through the car at the center of the underside of a truck whereby trackway actuators 105 located on a certain side of the track are arranged to vertically move actuator 104 and throw reverse switch 102 if a car is turned around. Actuator lever 104 is latched in position by usual means until an actuator 105 engages the low end of this lever. By this arrangement whenever a car is either operated in reverse or turned around the polarity of DYN is reversed.

Automatic Controls The car control portion of the intertrain control circuit is connected across resistor 59 and arranged to .be reversed by reverse switch 60 operated by either movement of reverse switch REV or actuator bar 109. Switch 60 comprises a circular drum shown developed flat revolvably supported to reverse the controls each time it is turned a particular even fraction of a revolution. The drum has notches in which a spring engaged rider holds the drum in position to prevent incidental turning as the car moves. Magnetic clutch 112 couples REV to reverse switch 60. Clutch 112 is engaged by the control current which throws REV in the usual manner so that whenever REV is thrown switch 60 is thrown. Switch 60 is connected so as to be thrown by and move actuator bar 109 pivotally secured at its middle in a horizontal plane to the bottom of a truck on the center line of the car so as to be turned by trackway actuator 105. Since switch 60 is coupled by clutch and turned by REV only while the vehicle is stationary, switch 60 is turned by bar 109 without ever turning REV. By this actuating arrangement switch 60 is reversed whenever either the car is reversed or turned around and operated over the same track past an actuator 105.

Operator switches determine the desired conditions of speed control namely: controlled, to be controlled (accelerated lor slowed) to substantially zero control current, which the operator can select by holding down switch 116 against spring pressure; controlling to not be controlled unless the control circuit requires stopping, selected by the operator holding down switch S0 against spring pressure; and neutraL to be retarded to zero control current (no switch for the operator) selected if neither or both controlled and controlling conditions are selected by the operator.

Automatic accelerating relay AR, stopping relay SR, and overcurrent stopping relay OSR are separately connected across segments 118 and 119 of reverse switch 60 in series with resistor 120 across resistor 59. The circuit for accelerating relay AR comprises in series from seg- 'nient 119, line 122, rectiiier 124 arranged to pass an accelerating current, normally open contacts 126 on controlled switch 116, coil of automatic accelerating relay AR, front contacts 127 on clear track relay CTR (optional), line 128, back contacts of relay OTR in parallel with normally closed contacts 129 of controlling switch 80 to segment 118. The circuit for stopping relay SR comprises in series across lines 128 and 122, coil of stopping relay SR, line 130, and rectier 132 arranged to pass a stopping current. The circuit for overload stopping relay OSR comprises in series from segment 118;

holding coil and front contacts of stick relay OTR; brush and slip ring 134, magnetic clutch 136, nger 137, and rheostat wire 138 of a distance-of-travel controlled rheostat 139; coil of overload stopping relay OSR; line 130; and rectifier 132 which again passes only a stopping current; line 122; to segment 119. The ypull-in coil of reay OTR is connected in series with rectiiier 140 arranged to pass a stopping current and front contacts of relay PCR across segments 118 and 119.

Relay CTR is preferably energized across the clear aspect circuit SCS of a cab-signal control system of any type such as those in general use. Front contacts 141 of relay CTR are connected across the back contacts of relays SR and OSR to enable a vehicle to accelerate when the track ahead is clear even though a stopping current is received from a rearward vehicle on the samesection of the control line. Front contacts 127 prevent automatic acceleration except when the track ahead is clear. Contacts 127 can be omitted from relay CTR. Relay CTR is optional, since it takes care of special situations which can be avoided and because where line 14 is divided into segments shorter than the space between collectors 24 on the closest spaced trains relays CTR are not needed. Contacts 141 do not interfere with operation of this systern where trackway control signaling for energizing relay CTR is not provided.

Stopping Delay The distance-of-travel controlled rheostat 139 is driven through magnetic clutch 136 from reverse-shift-and-speedreduction unit 142 from car wheels 94. Shift-and-reduction unit 142 is arranged to drive the rheostat from full to lowest resistance in both directions of vehicle movement by actuating a reverse lever 146 on unit `142 from reverse switch REV by means such as arm 147 extending from REV and linked to lever 146. Spring 14S returns rheostat 139 to full resistance position when clutch 136 is disengaged. Relay OTR controls the engagement of clutch 136. Relay OTR is arranged to be closed only when the intertrain control circuit is irst closed and a high value of intertrain control current passes therethrough as results from a train at speed coming into intercontrol with a standing or slow moving car or train. The resulting stopping current on the approaching train is closed through relay OTR and passed by rectifier 132. This stopping current holds relay OTR closed until a very low value of stopping current is reached. This current also closes clutch 136 which turns rheostat 139 reducing the resistance in series with relay OSR as the train progresses. If the train operator holds down controlling switch 80 with OTR lifted he opens the circuit to relay SR at contact `129, and as long as the stopping current is not too high relay OSR is not lifted and the train can proceed indicating that the car ahead is accelerating sufficiently or the speed difference between the train and car is safe relative to their distance apart. For the operators information ammeter AM is connected across resistance 59 to show the intertrain control current whereby the operator can see the car ahead accelerate. Rheostat 139 is so proportioned and driven as to convert the required safe reduction of maximum control current with distance to the substantially constant current value at which relay OSR operates. 1f the initial control current was not too high as to lift relay OSR the train can proceed as long as relay OSR or SR is not lifted. Relay OSR is only energized when it is necessary to stop or slow the train, as when the car ahead does not start or accelerate suiliciently relative to the speed of the train. It should be seen that a fast train will allow less time for a car ahead to start and accelerate than a slow train allows, `and a train can progress until stopping is needed with a safety factor varied only by variation of the zone of control. The resistance of rheostat 139 reaches its low value before the limit of its travel is reached. Approaching this limit of travel with the control current through relay OSR at about its pull-in value relay OTR drops before clutch 136 disengages. The dropping of OTR opens clutch 136, and spring 148 returns rheostat 139 to full resistance position. Relay SR is now connected through back contacts of relay OTR.

The pull-in circuit of relay OTR is opened to prevent relay OTR from picking up and initiating a delay of stopping when a strong stopping current is received when, for instance, a train is approaching a car at coupling speed (practically zero control current) and the control zone suddenly bridges to a standing car ahead. Such a situation would lift relay OTR allowing the train to run at unsafe speed into the car it is following were it not for relay PCR which closes the circuit of the pull-in coil of relay OTR only while the track ahead is clear and for a short ltime thereafter.

The coil of relay PCR is energized through a circuit which checks that there is no other train (open control circuit) in the zone of control before energizing relay PCR. While relay PCR can be energized by the clear aspect circuit SCS of a usual automatic train control or cab-signal system which could be provided with my system for trains not having the intertrain control (the track circuits and relays TR being utilized therein), it is preferred to provide a simple and fool-proof arrangement for detecting a clear zone of control which can be used Where automatic train control or cab signals are not provided and where the rails are not insulated apart.

Line 159, FIGURE l, is supplied with a frequency F3 by alternator F3 connected from line 150 to ground. The right-hand end of each control block is connected from the output side of the rectifier 26 between the block and the block to the right in series with front contacts of relays BR and BRl between these blocks in series, resistance 152, frequency F3 limited pass filter 154, to line 150.

On each train, FIGURE 2, frequency F3 is received by a circuit comprising in series trolley 24, segment 57 of reverse switch REV, contacts 86 on the coupling switch at the front of the train, line S8, line 156. full-wave rectifier 153 across the D.C. terminals of which is connected the coil of relay PCR, frequency F3 only pass iilter 160, ammeter AMZ (optional) to ground. The frequencies F1, F2, and F3 are sufficiently close and arranged to be passed by hand pass filter 74 from block to block along the control circuit within the zone of control.

By this arrangement frequency F3 put on the control line 14 at the right-hand end of the control zone is received by all trains equipped with intertrain control throughout the control zone. Resistance 152 is high relative to the impedance of the circuit for F3 on each train and the remainder of the circuit supplying F3, whereby relay PCR is arranged to close with full voltage of F3 on line 14 and hold when its energizing circuit is the only circuit drawing F3 within the zone of control and drop when the voltage is reduced (can be reduced to nearly half) by the presence of another train drawing F3 current within the zone of control.

When a train at speed cornes into intercontrol with a standing or slower moving train ahead with relay PCR lifted holding closed the circuit of the pull-in coil of relay OTR, relay OTR is allowed time to pick up before relay PCR drops. Then relay OTR is prevented from picking up again until relay PCR has lifted and OTR receives a heavy stopping current.

A unit uncoupled just before a train cornes into intercontrol with a car ahead to couple it at speed would prevent relay OTR from lifting, since relay PCR dropped when its current is reduced by the uncoupled unit drawing F3 current. The operator of such a unit should wait for intercontrol with the car ahead before uncoupling, so that the train will not needlessly be slowed. A trackway marker could tell him where intercontrol would be established on approach to a station from which the vehicle ahead is to be accelerated. With the clear aspect signal of a trackway control signal closing contacts 141 this situation is not encountered, since the presence of the uncoupled unit at the rear would not change the clear aspect for the train.

If it is desired to prevent automatic acceleration except when `the track ahead is clear contacts 127 are provided to close the circuit of relay AR only while a clear track signal is received by relay CTR. Manual acceleration subject to automatic stopping then enables a following car to couple a train.

If it is desired to allow automatic acceleration when the track ahead is occupied the following arrangement prevents a vehicle from being accelerated by a rearward vehicle into a forward vehicle at an unsafe speed. Across resistor 90 is connected normally closed contacts 162 of controlled switch 116. Across resistor 120 is connected normally open contacts 164 of controlled switch 116. Resistor 941 is inserted in series with `the main control circuit (bypass opened) when controlled switch 116 is pressed down thereby reducing any control current to encourage any accelerating current to take a path through any train tha-t might be within the control zone that is not ready to be automatically accelerated to reduce the speed to which the unit wherein switch 116 is closed can be automatically accelerated when a forward train or car within the control zone is not accelerated. Resistor 126 is bypassed when switch 116 is pressed down to enable a lessened total con-trol current to supply the same stopping current to the stopping relays SR or GSR as it would with switch 116 open. By this arrangement plus the current limiting series field 92 described, the vehicle cannot be automatically accelerated very much when there is one or more trains which cannot be accelerated in the zone of control even when a fast train enters. Further, a train entering a zone of control having two stopped trains will feed control current to both causing its stopping current to be extra large, more readily stopping the entering train. Also the value of the control cur-rent read on ammeter AM can tell the entering trains operator, taking into account his speed, whether there is one or more units ahead in the control zone, and the operator of a unit beginning automatic acceleration can read if there is `a standing unit ahead by a very fast reduction of his accelerating current and its reversal of direction at -low speed to a stopping current gradually stopping the unit as the train behind slows to a stop. With this arrangement (contacts 127 of relay CT R being omitted or jumpered) and with switches 116 and 80 closed the unit can be automatically accelerated by a forward train to couple it. 90, 120, and 92 are made `as large as needed.

Uncouplz'ng The operators uncoupling switch 170 connects battery 96 to uncoupling control valve 1172 through a check circuit which will not close if there is any control voltage supplied to line 1LE- by any following traic or by any forward tratlic moving toward the train within the zone of control. Switch 170 when closed by an operator against spring pressure connects the positive of battery 96 to line a connected through train line trunk T to line a', through segment 174 on reverse switch REV to contacts 176 on coupling switch CS or CS whichever is at the rear of the car as determined by REV and through the coupling switch closed on the rear of the train to line 178, front contacts 179 of relay 180, back contacts of relay 182, line b connected through train line trunk T to b', contacts 184 of switch Y1711 now closed by the operator on the car to be uncoupled, contacts 186 closed when the end passage between the forward car is locked closed and the car made ready for uncoupling, coil of solenoid valve 172 to ground all in series. The coil of relay 181) is connected from line 178 -to ground, so as to be energized on the rear car of a train when an operator closes a switch 170 on the train. Line 56 connecting trolleys 24 is opened on the last car of the train (or optionally on any car behind the front car) through back contacts of frelay 1811 ahead of the engaged collector 24. The coil of relay 182 is connected from collector 24- to ground in series with front contacts 188 of relay 180. Front contacts l179 close `after front contacts 188 and after relay 182 has had time to open, so that if there is traflic which sends an accelerating current this opens relay 182 preventing the completion of the uncoupling circuit-as long as relay 182 is energized. 1f the fore part of the train were on the same length 'of control line 14 this would prevent the unit from uncoupling until a rectifier 26 passed between the cars separated by an energized relay 188. Where trolley or third-rail shoes are provided at both ends of the car the uncoupling switch opens the circuit of the forward trolley to utilize the sectionalization of the control line to prevent control between the train and the uncoupled unit, one arrangement whereby the coupling switch opens the forward trolley being shown and described with FIGURE 16'. A car having a complete control station at each end would have two sets of uncoupling circuits and operator switches.

When the circuit to valve 172 is closed the unit is uncoupled. When the coupling pin is fully lifted it closes contacts 194 connecting a circuit from positive of battery 96, line 103, line 196, contacts 194, pull-in coil of stick relay 198, to ground. An uncoupled-car stopping circuit is closed from the positive of battery 96, line 103, line 199, front contacts of relay 280, front contacts and hold coil of relay 198, coil of uncoupling stopping relay USR, to ground. The coil of relay 2110 is connected across generator 202. Generator 2112 is driven according to car speed from drive 9S so as to energize relay 200 and hold the stopping circuit closed to energize relay USR down to a low car speed whenever stick relay 198 closes, indicating that the car is uncoupled from the forward car of a train. Operator controlled vlaves or check valves in the ends of the :air hose lines shut oilc the air between uncoupled cars.

Master Controller Drive Cani shaft or drum controller' 268 is driven by pilot motor PM through worm 210 on the 'motors shaft engaging worm gear 211 secured on shaft 212, spur gear 213 secured on shaft 212 engaging spur gear 214 secured on the shaft of controller 268 providing speed reduction from motor PM to controller 2118 with shaft 212 driven at an intermediate speed. The cam of a controller positining cam switch 216 is secured on shaft 212, and the cam of a controller olf-position switch 217 and controller full-speed position switch 218 are secured on the controllers shaft. lPilot motor PM is preferably driven from battery 96 insuring that the pilot motor can return to olf position with the power off. Motor PM could have a permanent-magnet eld or else as shown have its field coils 220 connected across battery 96 in series with front contacts 221 on pilot-motor operating relay 222, contacts 221 having in parallel therewith normally open contacts 223 on control switch KS. The pilot motors armature is connected to drive drum 203 to start and accelerate the vehicle by a circuit from the positive of battery 96, contacts 223 of switch KS or front contacts 221 of relay 222 in parallel, front contacts 225 on 'pilotmotor reversing relay 226 which controls the notching up and down of contactor 263, armature of the pilot motor, front contacts 227 of relay 226 to the ground side of battery 96. The pilot motors armature is connected for deceleration and stopping by the circuit from the positive of battery 96, front contacts 229 of relay 222, back contacts 230 of relay 226, armature of pilot motor PM, back contacts 231 of relay 226, back contacts of relay HR, to the ground side of battery 96. The coil of pilot motor operating relay 222 is connected across battery 96 in series with contacts of off-position cam switch 217 opened only in off position of controller 288. Stepposition cam switch 216 opens its contacts on each controller step or contact position of drum 2118 and is connected in parallel across the back contacts of relay HR. Full-speed switch 213 on controller 208 opens at full speed position dropping relay 226.

Control Power Limited T0 Headf End So that only 4the car at the head end of a train may be in control, a segment 232 `on .the :operators reverse switch REV connects line 234 from the positive of battery 96 to head end control supply line 236 through contacts 238 on coupling switch CS or CS' whichever is at the front as determined by REV. Contacts 238 are open between coupled cars and closed only when there is no car coupled to the end on which coupling switch CS or CS is located. Thus line 236 is connected to battery 96 only on the leading car. Line 240 connects power from line 236 through front contacts of relay BR to drum 208 and to the coil of relay TLR which when energized closes the circuits from drum 20S to respective train lines of trunk T. Relays TLR isolate the train lines from the drums 208 which are not on the leading car, so that as soon as cars couple only the leading car will be in control, and so that train lines cannot feed power to drum 20S. The removal of power from train line T1 (by the dropping of relay BR) applies the brakes. If the leading car is out of service the coupling switch contacts 233 which are at the front of another car can be jumpered. lf it is desired to back up a train the reverse switch segment 232 can be jumpered to the coupling switch contacts 238 which are at the rear. When such jumpers are used a manually-closed spring-opened switch would be in series with each jumper.

Accelerating, Holding, and Braking Circuits The accelerating circuit comprises in series from the control-power beeldend-selecting line 236, line 242, front contacts on holding relay HR, normally open contacts 244 on spring opened operators control switch KS in parallel with front contacts of accelerating relay AR and normally open contacts 246 of spring opened automatic-control switch 116 in series, full speed switch 218 opened at full speed position of drurn 208, and coil of relay 226 to ground. The holding circuit comprises in series from line 236, front contacts of check relay CR, operators brake applying switch BS, back contacts of relay USR, holding switch contacts 243 engaged in through full-closed position of operators control switch KS, back contacts of' relays OSR and SR, and coil of holding relay HR to ground.

Though brakes are applied when the controller 208 reaches ott position by opening power to train line T1, it is preferred that brakes be applied immediately when needed by either the operator or automatic control without waiting for the pilot motor to return drum 208 to olf position. Accordingly brakes are applied by opening the circuit to the coil of relay BR connected in parallel across a portion of the holding circuit. The coils of relays BR and HR could be in series, but it is preferred not to apply the brakes when a control circuit stopping current is received if reduction of power to the motors will correct the speed difference. Therefore the coil of relay BR is connected to the holding circuit ahead of contacts 24S of KS in series with back contacts of relays SR' and OSR whose coils are connected across the coils of relays SR and OSR respectively so as to operate at a heavier control current than relays SR and OSR respectively. When only a slight speed correction is needed relay SR or OSR operate and relay SR and OSR' remain closed. When brakes must be applied to correct the speed difference relay SR or OSR also opens. It should be noted that whenever relay BR drops relay HR drops or has dropped to return the pilot motor to ol position. The opening of the holding circuit returns drum 203 to off position.

Interruption of Normal Controls After Uncoupling Upon uncoupling a unit of one or more cars from a train the check circuit on the uncoupled unit is arranged to be opened for an interval at back contacts of relay COR. Relay COR could be energized by connecting its coil in series or parallel with the coil of relay USR, or as preferred and shown the coil of relay COR is energized for a time interval, effective even when the car is uncoupled when standing still, by time delay relay TDR. The coil of relay TDR is connected from line 236 to l. ti

ground so as to be energized when the coupling switch at the front of the car closes as the unit is uncoupled from the train. The coil of relay COR is connected from line 236 to ground in series with back contacts on relay TDR. During the delay period relay COR holds open the check circuit on the uncoupled unit dropping relay CR energizing warning light 250 and buzzer 252 connected from line 236 through back contacts of relay CR to ground and opening the holding circuits to relays BR and HR respectively applying brakes and returning the pilot motor. The last car of the forward train drawing check current having passed beyond the block occupied by the uncoupled unit, the control line 14 is grounded in the block occupied by the uncoupled unit through line 52, choke 66, back contacts of relays TR and DCR of that block to rail 11, grounding through rectiers 26 all block sections of line 14 bridged together relative to tratlic from either direction approaching the block occupied by the uncoupled unit. Back contacts on relay TDR open the current supply to the coil of relay COR after the delay period dropping relay COR. Relay USR being energized through the uncoupling circuit holds open the circuits to the coils of relays BR and HR after the delay period until the uncoupled unit reaches a low speed at which relay 200 drops dropping relay USR releasing the brakes and returning accelerating control to the operator.

Manual Switch Arrangement Controlled switch 116, as shown in FIGURE 3 has secured thereto a side extension 254 arranged to close switch KS halfway when switch 116 is closed full. When the operator presses KS down about halfway contacts 248 close the holding and brake releasing circuits, and contacts 223 close. When he presses KS all the way down the car is accelerated with holding contacts 248 and accelerating contacts 244 of KS closed. Thus contacts 223 and 248 are closed by either switch KS or 116, and the operator at the head end of the train by resting his hand on switch 116 holds KS closed halfway when waiting for and during automatic control.

Operativi: of tlze Controller When an accelerating current is received from a train approaching from the rear (the polarity of a train approaching from the front provides a stopping current) relay AR closes. Then with switches 116 and BS closed, relay CR energized, and pilot motor PM in off position of the control, relay 226 is energized driving the pilot motor to turn drum 203 to accelerate the unit. When the unit accelerates to the speed of the following train the accelerating current drops to zero dropping relay AR, which drops relay 226 (unless the operator chooses to accelerate his unit by closing switch KS) causing the pilot motor to return to the last notch position of drum 208 whereat switch 216 opens stopping the pilot motor and holding the car controls on this running notch. If it is undesired that all notches be selected by the operator because of the resistance loss when running on these notches the cam of notch position cam switch 254 is secured on the shaft of drum 208 to open only at manual running positions and connected in series with contacts 256 on the operators control switch KS across the contacts of notch cani switch 216, contacts 256 being arranged to close after considerably past halfway but before KS is fully closed. The car will continue to accelerate, since it takes time for the traction motors to reach full speed for a given voltage applied. When the unit exceeds the speed of the train trying to couple it a stopping current is received lifting relay SR which opens the holding circuit dropping relay HR closing the circuit for the pilot motor to return. As the pilot motor returns and the unit starts to slow down the stopping current dies out, relay SR drops, relay HR is energized, and the pilot motor stops drum 208 on the highest notch remaining closed. By similar' operation the pilot motors on both parts in various variations.

17 the unit and train are controlled to closely maintain balancing speed (zero control current) at which the train can follow or couple the unit ahead as the trains operator desires.

Variations In the variations to be considered hereinafter like parts have the same reference numerals. Many details shown in FIGURES l-3 are not shown in the variations, but it should be evident that these parts and features can be added and variations of parts can replace corresponding Pass filters are those which attenuate all frequencies which may be encountered except those which are specied tol be passed thereby.

Wherever it is impractical to insulate apart the track rail-s 11 and 12 as on street railways or undesirable to install or use existing track circuit blocks for this control system the control blocks are confined to the control conductor or conductors. One such arrangement is shown in FIGURE 4 together with further variation over FIG- URES 1 and 2 in that the control circuit is opened on a unit for an interval after uncoupling from a train with conditions safe, thus dispensing with the need for dividing control line 14 into segments 16 to interrupt the control between the train and uncoupled car.

Referring to FIGURE 4, control line 14 is divide/d into block lengths A2, B2, C2, etc, insulated apart by insulators 18. Each control block has a block circuit supply transformer 260 whose primary is connected across supply lines 262 and 263 and whose secondary is connected from ground to the left-hand end of line 14 in that block in series with filter 264 arranged to attenuate all currents except the block supply current. Each block has coils of control line block bridging relays BR2 and BRS connected from the right-hand end of their block length of line 14 to ground, both in series with filter 266 passing only the current from the transformer 260 connected to the same block. Back contacts on relays BR and BRS bridge the block from which the are energized to respectively the right and left-hand adjacent block. Relays BR2 and BRS between adjacent blocks bridge across the control line insulator 18 therebetween in parallel and both in series with impedance coil 32 and rectifier 26. Relays BR2 and BRS have front contacts which connect power from line 268 to the coils of respectively relays BR4 and BRS arranged to bridge through back contacts the far end of the next block respectively to the right and left in parallel with the back contacts of the relays BR2 and BRS which bridge these blocks. A circuit from trolley 24 to ground on each vehicle connects the coil of relay CR through filter 270, which passes current from transformer 260 only, to ground a sufficient amount of block circuit current to cause relays BR2 and BRS to drop when a train enters their block, dropping relays BR4 and BRS which were energized therethrough bridging a series of blocks into a zone of control'.

If it is desired to provide two-directional control current, signal generator or alternator F1 engaged by controlling handle 8? is again connected from trolley 24 to ground in series with frequency selective circuit 82 tov prevent grounding of other frequencies therethrough. This signal is arranged to energize relay TCRl connected in series with filter 71 from the ri ght-hand end of each block length of line 14 to ground for traffic movement from left to right where cars are accelerated to couple trains and is omitted where not desired as between blocks B2 and C2. Front contacts of relay TCR1 are connected across rectifier 26 at the exi-t end of the block to which that relay TCRI is connected, whereby two-way control current can pass insulators 18 when relays TCRl are energized by the train operator closing switch 80` to slow a unit ahead to couple it.

Along track a is shown train 20a-21a and train 22a which has uncoupled therefrom. The control circuit for each train from collector 24 to` point J comprises in series, segment 57 of traction power reverse switch REV, contacts 86 on the coupling switch CS or CS whichever is at the front of the train according to the position of REV, line 88, back contacts 272 of control circuit opening relay COR', and A.C. choke coil 59'. vThe automatic train controls for FIGURE 4 connected from point J to therails can be considered the same as those shown in FIGURE 2 from point I to the rails and therefore are not repeated but represented as ACC2 in FIG- URE 4.

1n parallel across back contacts V272 of relay COR', rectifier 274, arranged to pass a stopping current, is connected in series with front contacts of relay COR and contacts 276 and 277 on reverse switch 60. Relay COR is energized by the circuit from the positive of battery 96, segment 232 on REV, contacts 238 on the front coupling switch CS or CS as determined by the position of REV, line 236, back contacts of relay TDR, the coil of relay COR', and ground return to the opposite side of battery 96. The coil of relay TDR is connected from line 236 to ground.

On each train a check current is supplied by signal generator or alternator F4 connected from the control Iline side of impedance 59 to ground in series with F4 limited pass filter 284i and back contacts 281 of relay COR which open this check circuit during the time delay period of relay TDR commencing upon the uncoupling of the unit from the train. A control grounding relay CGR is energized from this check signal F4 of generator F 4 through filter 286, back contacts of COR', line 88, contacts 86, segment 57, trolley 24, control line 14, line 282 in each block occupied by the train, F4 pass filter 283, full-wave rectifier 284 across the D.C. terminals of which the coil of relay CGR is connected, to ground return to alternator F4'.

When unit 22a uncoupled, contacts 86 on coupling switch CS at the head end of the unit closed, connecting the coil of relay COR to battery 96, lifting relay COR', opening the control circuit relative to the faster moving forward train, and closing the control circuit through rectifier 274 relative to a slower moving forward train. If relay 180, FIGURE 2, were now energized on the forward train the uncoupled unit would send a control current through rectifier 274 to the rear car of the forward train which would hold open relay 182 and so prevent -a second unit from being uncoupled from train 20a-21a until the train passes beyond the zone of control of the uncoupled unit or the uncoupled unit practically stops. Relay COR when lifted during the delay period, also opens the circuit of alternator F4', dropping relay CGR in the blocks occupied by the unit after the forward ytrain has passed beyond these blocks.

A unit uncoupled from a train grounds the blocks be hind preferably the forward block occupied by the unit to the end of the zone of control with respect tothe D.C. control circuit of following vehicles and grounds the A.C. block current of all blocks occupied during the delay period for a time longer than the delay period of relays TDR. When unit 22a moves into black B2 train 20a-21a having moved beyond block B2, block A2 will have a D.C. ground and block B2 will have a grounded A.C. block circuit. The D.C. grounding circuit comprises from line 14 block A2, line 286, back contacts 287 and 288 on respectively relays CGRl and CGR block 2, choke 66 block B2, resistance 290, all in series to rails and ground. Resistance 290 enables a signal to be received from an uncoupled unit occupying a grounded block, which will prevent the train 20a-21a from uncoupling a second unit before the rst has slowed down sufficiently. The coil of relay CGRI block B2 is connected in parallel (or series) with the coils of relays BR2 and BRS of block B2 so as to also drop when the check current drawn by relay CR of a train occupying block B2 drops relays BR2 and BR3 thereof. The A.C.

19 grounding circuit comprises in series from line 14, line 282, block circuit current limited pass filter 292, back contacts 293 on relay CGR1, coil and back contacts of time delay relay TGR, back contacts 294 on relay CGR, resistor 295 across which is connected a red signal lamp R, to ground. The grounding of the block current of block B2 keeps relay CGRl from being reenergized after unit 22a passes to block C2 until time-delay relay TGR opens after delay relay TDR on the unit has had time to open, completing the check circuit of the unit, raising relay CGR, unshorting the block or blocks then occupied by the unit, the remaining shorted blocks being opened by the lifting of relays TGR arranged to open enough to allow relays CGRI to open.

Cars of FIGURE 4 can be arranged to operate on the trackway of FIGURE 1, and the car shown in FIGURE 2 can have an alternator F4 added and be arranged to operate on the track of FIGURE 4.

Where it is desired to utilize the control line for traction currents or conversely a power distribution conductor as the control line the control circuit is varied and adapted to supply traction power to each section of the control line through an arrangement which prevents the control current from using feed or return conductors to go from block to block and by separating the traction from the control power on the cars. While A.C. traction power can be separated from D C. control power, one arrangement being later described with FIGURE 10, it is preferred to provide an A.C. control circuit such as shown in FIGURES 5, 9, or l2 when A.C. or D.C. traction current is to be supplied on the same contact conductor with the control voltage. The A.C. control current is of a different frequency from the A.C. traction current so as to be separable therefrom.

Referring to FIGURE 5, along track b is run trolley wire 14a to provide electric motive power, speed control signaling, and a control synchronizing frequency for selfpropelled rail units such as cars 2Gb and 22b represented by their wheels and axles on track 10b.

With rails 11b and 12b of track 10b insulated apart line 14a need not be divided by insulators into block lengths. Track 10b is divided by insulators 36 into double-rail track circuit blocks represented by blocks A3, B3, and C3. The track blocks are sufficient to limit the extent of the zone of control where the track is well ballasted, drainage is good, and the control voltage is kept low. Leakage past rail insulators could only extend the zone of control,

Each block can be considered similar to block B3 wherein the secondary 29S of track-circuit transformer 299 is connected across the rails at the left-hand end and track circuit relay BTR is connected across the rails at the right-hand end, all as usually provided in a track circuit. Each relay BTR closes through back contacts an electrical bypass or bridge circuit from the block across which relay BTR is connected to the adjoining block at the right across insulator 36 in rail 12b. This bypass includes back contacts 300 of relay BTR in series with a synchronous-rectifier unit SRU wherein rectifier 26a is arranged to pass return control current of a particular phase sequence and block current 180 out of phase therewith. Back contacts 301 of relay BRG are connected across back contacts 300 of relay BTR. Relay BR6 is energized through front contacts on relay BTR one block to the right; and, if more blocks are desired to be bridged, relay BRG can be energized through front contacts of relays BTR of a series of blocks to the right as shown for relay BR FIGURE l. Relay BR6 block B3 is energized through the circuit comprising from supply line 302, line 303, front contacts on relay BTR block B3, coil of relay BR6, to line 304. Lines 302 and 304 also supply the primary of transformer 299 connected thereacross.

Synchronous rectifier SRU comprises a two segment commutator across which rectifier 26a is connected, secured, and rotated by synchronous motor SM at a speed Cil whereby rectifier 26a is reversely connected to brushes d and d engaging the commutator apart so as to cross segments every half cycle of the control circuit voltage as the control voltage passes through zero and half phase in phase therewith. These synchronous rectiers permit A.C. control current to pass between approaching trains and completely block control current between receding trains. Synchronous motor SM is selected to be a two-pole motor and is connected across coil 306 of transformer 299 which is energized from the same source that supplies the synchronizing current to the trains. A positive drive speed increaser 307 connects motor SM to rectifier unit SRU for receiving the rectifier every half cycle in step with the control circuit voltage.

A check circuit optionally provided for checking that blocks are bridged comprises in series as shown between blocks A3 and B3, secondary 308 of transformer 299 block B3, back contacts 309 and 310 of respectively relays BTR block A3 and BR6 block B3 in parallel, signal lamp W3, rail 12b block A3, bridging contacts 300 and 301 respectively of the same relays BTR and BR6 in parallel, synchronous rectifier unit SRU, rail 12b of block B3 to the opposite side of coil 308. This circuit checks the complete bridge circuit including the bridging conductors, their connections to the rails, and relay bridging contacts.

Two-way control signaling again can be provided by providing on the cars frequency F1 by means of generator F1 connected from pantograph 24'zz to ground in series with F1 pass filter 82a and operators switch contacts 79, and by providing relays TCR along the trackway. Front contacts of relay TCR block B3 are connected in parallel with rectifier unit SRU. Relay TCR block B3 is connected across D.C. terminals of bridge rectifier 70 whose A.C. terminals are connected from control line 14a to rail 11b block B3 in series with F1 pass filter 71a and current limiting resistor 311. The range of F1 need not be great, since trains will usually be close together before the fine speed adjustment feature of twoway control is desired.

Impedance bonding between adjacent blocks provides a path for the `return propulsion and synchronizing currents. The impedance coils 312 and 313 are connected as usual across the rails of adjacent blocks, `but the center taps of the coils of adjacent blocks are connected together through a parallel-resonant circuit comprising impedance coil 314 and condenser 315 in parallel across the center taps of coils 312 and 313 of the impedance bond between adjacent blocks. The resonant frequency of the coil and condenser is such as to attenuate the A.C. control signal frequency.

A.C. or D.C. traction power is supplied to line 14a across terminals e-e connected in series with attenuator 316 tuned to block the frequency of the control current from contact conductor 14a to the center tap of impedance coil 313 block C3. The D.C. dynamo of the preceding examples is replaced on each rail unit by a shunt or separately excited A.C. generator or dynamo ACD driven by a synchronous motor SM1 through positivedrive speed increaser 307a arranged to synchronize dynamos ACD in phase on all trains. Dynamo ACD has a frequency output a whole plural multiple of the frequency Fs of motor SM1; whereby, with a given field polarity, the A C. dynamos on all the trains on the system are synchronized substantially in phase with each other for movement in a given direction along the track. Motor SM1 is connected from the pantograph 24a engaging line 14a to the wheels of each powered unit in series with a series-parallel tuned filter 318 arranged to pass the frequency of motor SM1 and attenuate the frequency of the dynamo ACD, traction power, etc. Where A.C. traction power is provided it can be used to drive the synchronous motors. Where a different frequency for motors SM1 is desired or where D.C. traction power is provided A.C. is also supplied across terminals e-e to conductor 14a for the synchronous motors. The dy narnos frequency is selected, but not limited, to be three times that of its drive motor; which, for eXample, is operated on 6G cycles, providing 180 cycles dynamo frequency. The larger the number of times the control frequency is relative to its synchronizing motors frequency the greater any phase difference between motors SM1 would be magnified between dynamos ACD. Therefore the frequency multiplication between motor SM1 and dynamo ACD is preferably low vbut yet high enough for satisfactory separation by filter circuits. Each dynamo ACD is separately excited by a D.C. exciter DCE driven from a traction motor or axle, whereby the effective electromotive force of dynamo ACD represents car speed. A speed diiference between trains is represented by a current between trains resulting from a control voltage ditference between dynamos ACD on the different trains.

Since dynamos ACD are synchronized in phase on all the cars, they can be coupled together *between cars in parallel across the control conductor and the rails similarly as if D.C. dynamos were used. At each instant, except when the dynarnos ACD go through zero voltage, their relative output voltage represents speed as with D.C. dynamos. A Wattmeter or rwattmetric relay WR is connected with its potential coil across the output ot each dynamo and its current coil in series with the control circuit of the dynamo whereby relay WR determines, except in a particular situation to be `discussed with FIG- URE ll, whether the dynamo is operating as a generator or motor, i.e. whether the dynamo is delivering current or receiving current respectively. The circuit of dynamo ACD comprises in series from the current collector to the rails 180 cycle pass iilter 326, synchronous rectifier unit SRU1 in parallel with tback contacts of relay COR', current 4coil of Wattmeter relay WR, current limiting tield and armature of dynamo ACD, to ground. The primary of the main transformer for A.C. traction or the traction motors for D.C. traction are connected across terminals f-f from the pantograph to the rails in series with an attenuator 322 of the 180 cycle control current and F1, F2, etc. currents. Attenuator 322 comprises one or more parallel tuned circuits and with the aid of the 60 cycle pass 318 and any other filters needed substantially prevent 180 cycle power from being lost before and after transmission.

Wattmeter WR is the zero centering type and is connected so as to turn to the right or left to accelerate or stop the vehicle when the dynamo on the vehicle is motoring or generating respectively. The relay WR has a sliding contact arm 324 `which connects power from line 236 to the coil of accelerating relay AR when arm 324 turns to the right and connects power to the coil of relay OSR through rheostatic resistance 326 and to the coil of relay SR and to the circuit of the coil of relay USR when arm 324 turns to the left. Additional relays OSR and SR can be added in series with resistance 326 to operate at different values of control current. The portion of resistance 326 in series is decreased as contact arm 324 swings to the left from center.

Exciter DCE reverses polarity when operation is reversed causing a 180 phase shift of the dynamo, so that two vehicles approaching each other from opposite directions one in reverse and the other in forward will both be stopped. If vehicles are turned around and operated over the same track the main iield of dynamo ACD is connected through contacts of reverse switch 102 whereby trackway actuator 15 controlling switch 1il2` establishes the proper polarity whereby cars approaching from opposite directions are both stopped inde-pendent o-f Whether reversed or turned around. Switch 102 could be inductively operated from means located along the rails or trolley wire or even could be manually operated.

Synchronous rectifier unit SRUl is similar to synchronous unit SRU. The commutator of unit SRU1 is secured to rotate with dynamo ACD so as to reverse polarf' hand block ends.

ity in step with each half-cycle reversal of dynamo ACD. Since the dynamos frequency is selected to be three times that of motor SM1, with a two-pole dynamo and a twosegment rectiiier unit both can be driven on the same shaft by a positive drive speed increaser from motor SM1.

As an alternative to using speed increasers, the synchronous rectiiiers SRU and SRUI could be replaced each with rectifier unit SRUZ, FIGURE y6, which has a sixsegment commutator 33t) with motor SM or SM1 directly connected and rectiiiers 2Gb connected and secured across opposite segments reversely from adjacent segments to reverse polarity every 6th of a revolution in step with the control frequency.

Where it is not desired to use or provide track circuits to limit the zone of control the combined control and power supply conductor 14n is divided into control circuit blocks with traction power fed to each block through means which prevents the passage of control current etc. from block to blo-ck therethrough.

A control line block arrangement for supplying D C. traction current to adjacent block sections of a control conductor is shown in FIGURE 7 where D.C. current is supplied from line 334 through impedance coil 335 to the center tap of impedance coil 336 the ends of which are connected across adjacent block sections A4 and B4 of control line 14h. This impedance bond prevents passage f of AC. signal current from one "block to another and tO line 334 but permits D.C. passage from line 334 to either or both control blocks connected thereby. Block bridging relays BR7 and BRS are connected from supply line 334 each in series with a series-parallel tuned circuit 338 arranged to pass the synchronizing frequency to motors SM1 on the cars to respectively the left-hand and right- A block bridging circuit is connected across adjacent block ends and has in series synchronous rectifier SRU3, arranged to pass first half cycles of control current from left to right and second half cycles from right to left from block, to block and front contacts of relays BR7 and BRS in parallel, whereby whenever a car takes synchronizing current for motor SM1 from a block the block relays BR7 and BRS at opposite ends of the block wherefrom the vehicle takes power are energized and bridge that block to adjacent blocks. Since coil 336 would pass equal synchronizing current to each adjacent block, as when one or more trains `draw current lfrom adjacent blocks, coil 335 is provided to block this current so that relays BR7 and BRS will be sure to close. Front contacts of relay TCR1 bypass rectifier unit SRU3 for two-way control signaling between trains. Relay TCRl is energized by frequency F1 sent from a train and passed by series-parallel tuned filter 71.

A control line block arrangement for supplying A.C` or D.C. traction current to adjacent block sections of the control conductor is shown in FIGURE 8 where A.C. or A.C. and D.C. current is supplied through impedance bonds 340 to blocks A5, B5, and C5. Impedance bonds 340 each have three coils 341, 342, and 343l of the same number of turns on a core. The central coil 342 is connected from supply line 344 to an end of each of the other two coils arranged to counteract the linx of the central coil. The other ends of the outer coils are connected one to each adjacent block end of block sections of control line 14a. This impedance Ibond does not pass the A.C. signal current from one block to another, since current in series through both outer coils induces a sum iiux in the core of the impedance. Bonds 340 permit A.C. or D.C. traction current to pass `from supply line 344 to either or both iblocks coupled to its outer coils, since the current in the center coil is equal to the sum of the branch currents in the outer coils and the flux of the center coil is neutralized by the outer coils. Block bridging relays BR9 and BR10 are provided at respectively the right and left-hand end of each block. The coil `of relay BR9 is connected from line 14a in its block to ground in series with F4 pass filter 348 `which passes frequency F4 differing from the traction current and drawn by motors SM1 on the trains of FIGURE 5. Line 349 supplies F4 to line 14a in each block through a resistance 350 and F4 pass filter 351 in series. If Fs differs from the traction current F4 can equal Fs. The coil of relay BRIG block B5 is connected from line 14a block C5 to grOUIld in series with F4 pass filter 352, and front contacts of relay BR9 `block B5. Block A5 is bridged to block B5 through back contacts of relays BR9 and BRI() in parallel and of respectively blocks A5 and B5. Similarly block B5 is bridged to block C5 through lback contacts of relays BR9 and BRIO of respectively blocks B5 and C5. Relays BR9 and BRI() drop when a train draws from the blocks feeding these relays current F4 separated respectively by filters 348 and 352 from the traction current. Frequency F4 differs from any A.C. traction current supplied so that it can be relatively shorted by the trains sufiicient to drop relays BR9 and BRll). F4 current drawn by a train in a block increases the voltage drop across resistor 358 in that lblock sufficiently so that relays BR9 and BRM) controlled thereby are dropped. A check circuit is shown for the bridge between 'blocks A5 and B5 and comprises in series secondary of supply transformer 354,1back blockbridging contacts of relays BR and BRI@ of respectively blocks A5 and B5 in parallel, and signal lamp W4. Rectifier unit RU of any suitable type is added in series with the bridge path 'between blocks A5 and B5 where cars are uncoupled at speed and stopped.

Control-line, or more generally trackway, rectifiers or rectifier units are primarily utilized to block the speed control current between an uncoupled unit and the forward train and can be omitted beyond the zones of control extending forward from each and every block in which units are uncoupled and stopped. Acceleration away from another vehicle not separated by a trackway rectifier can be provided by allowing acceleration on a clear track signal.

The attenuators preferably do not have series condensers where they must pass traction currents. Also I avoid blocking a condenser with a rectifier except a synchronous rectifier.

With the aid of `FIGURE 9 another arrangement for polarizing an A.C. intertrain control current and another arrangement for separating traction from control current will be described. Only the first half of each cycle of control current is selected to be transmitted by the trains c and 22e except when twoway control is desired when the full cycle is transmitted. On each train a synchronous commutator SC driven by motor SM3 passes alternate half cycles and blocks the other half cycles. The same half cycles are passed on all trains in either direction of operation through a circuit comprising from current collector 24C, line 356, D.C. or A.C. traction voltage bucking generator 358, brushes g-g engaging commutator SC which has insulator inserts 360 about its otherwise conductive circumference so as to alternately connect and disconnect brushes g and g on alternate half cycles, reverse switch 60 across which is reversibly connected rectifier 274 arranged to pass a stopping current, current coil of wattmeter relay WR, armature of dynamo ACD to the rails. Back contacts of relay COR are again connected across rectifier 274 to be opened for the delay period of relay TDR FIGURE 4.

D.C. or A.C. traction voltage bucking generator 358 is driven by motor 364 connected in series with a control frequency attenuator 366 and optionally a variable resistor 368 from trolley 24C to ground whereby the generator develops a voltage approximately equal to the traction supply voltage at the car. For A.C. traction generator S and motor 364 are both synchronous machines with the field of generator 358 varied with line Voltage preferably by connecting its field 370 or a portion thereof across a D.C. exciter 372 driven by A.C. series motor 374 connected from trolley 24e to ground in series with 24 control frequency attenuator 366 arranged so that voltage of generator 358 equals and varies with line voltage. For D.C. traction, motor 364, preferably a shunt motor, varies the speed of generator 358 with variation of line voltage so that generator 358 counterbalances the traction voltage in the control circuit preventing passage of traction current through the control circuit on the car.

Since only the first half of each cycle of the control current is used, the other half can be transmitted for other signaling purposes. Two-way control signaling is provided by bypassing brushes g-g through normally open contacts 376 of switch in parallel with a path including normally closed contacts 378 of switch 80, holding coil and front contacts of relay 380, and coil of relay 381, all in series across brushes gg'. A second synchronous commutator SC2 closes contact between brushes lz and lz during the second half of each cycle when brushes g-g' are electrically separated. Commutators SC and SC2 are positioned `and secured on the shaft of synchronous motor SMB which is connected from trolley 24C to ground in series with frequency Fs pass filter 318. A circuit is connected from the ground side of generator 358 to ground through normally closed contacts 382 of switch 80, brushes h-lz engaging commutator SC2, pull-in coil of relay 380, and back contacts of relay 381. When switch 80 on train 22C is closed by an operator, commutator SC is bypassed through contacts 376, and both half cycles of each cycle of the control current can pass from dynamo ACD of train 22e to trolley Wire 14e. Trackway rectifier 26 can then pass half of each cycle irrespective of the phase sequence of the current, i.e. independent on whether the faster train is behind or ahead of another. A forward train 20c completes the polarized control circuit when slower moving relative to train 22C through brushes g-g'. Forward train 20c completes the two-way control circuit when the second half of control current cycles are received. If trains 20c and 22e` were not separated by rectifier 26 the second half of the cycles of control current would be received by train 20c when the operator on train 22e closes switch 80 while train 22e` is in motion above a minimum speed in either direction, switch 80 on train 20c being open. With one or more rectifiers 26 in the intertrain control circuit the second half of each cycle (being negative for a train moving from left to right) would not be passed by rectifier 26 unless train 22e travels slower than train 20c. Whereupon the second half of each cycle on train 20c being more negative than that of train 22C then enables train 22e` to send a current past rectifier 26 to train 20c. The reception of the second half of control current cycles by train 20c energizes stick relay 380 which closes and holds twoway control closed through its front contacts. The closing circuit is preferably opened by relay 381 to prevent cyclic energy loss through the closing circuit.

These features illustrated in FIGURE 9 can replace the synchronous rectifiers SRU and SRU1 and various filters of FIGURE 5 permitting the use of stationary rectifiers 26 in place of synchronous rectifier units SRU along the trackway.

The operations of wattmeter WR and its limitations in the control circuit are illustrated by FIGURES 10 and ll wherein train 22d is traveling to the right and train 20d FIGURE l0 is traveling to the left at about the same speed. During the first half of each cycle dynamo ACD of train 22d is positive and of train 20d negative at the control line side causing a strong stopping current to fiow through both trains as indicated by arrows. Wattrneters WR on both trains read stop with both the current and voltage coils of the two wattmeters passing current in opposite directions as shown. If train 28d were slowed down relative to train 22d, at some slow speed of train 20d relative to 22d the current through the voltage coil of WR of train 20d would reverse as illustrated by FIGURE ll. When a dynamo 

